The present study evaluates the relative effectiveness of three types of input-based approaches for teaching English polite request forms to sixty Japanese learners of English: (a) structured input tasks with explicit information; (b) problem-solving tasks; and (c) structured input tasks without explicit information. Treatment group performance was compared with control group performance on pre-tests, post-tests, and follow-up tests consisting of a discourse completion test, a role-play test, a listening test, and an acceptability judgement test. The results revealed that the three treatment groups performed significantly better than the control group. However, the group that received the structured input tasks with explicit information did not maintain the positive effects of the treatment between the post-test and follow-up test on the listening test component.